1. Field of the Invention
The present invention relates to a wired circuit board and a producing method thereof and, more particularly, to a wired circuit board such as a flexible wired circuit board or a suspension board with circuit and a producing method thereof.
2. Description of the Related Art
A wired circuit board such as a flexible wired circuit board or a suspension board with circuit includes, e.g., an insulating base layer made of a polyimide resin or the like, a conductive layer formed on the insulating base layer, made of copper or the like, and including wires and terminal portions, and an insulating cover layer formed on the insulating base layer and made of a polyimide resin or the like to cover the conductive layer. Such a wired circuit board is widely used in the field of various electric and electronic equipment.
For the purpose of preventing migration in a conductive layer, a suspension board with circuit 31 as shown in FIG. 5(a) is proposed as such a wired circuit board, in which, e.g., a nickel thin film 35 is formed on the surface of a copper conductive layer 34 formed on an insulating layer 33 supported by a stainless steel foil base material 32 to cover and protect the surface of the copper conductive layer 34 (see, e.g., Japanese Unexamined Patent No. 10 129831 10-12983).
In the production of the suspension board with circuit 31 described in Japanese Unexamined Patent No. 10-12983, the nickel thin film 35 formed on the surface of a terminal portion 38 exposed from an opening portion 41 in an insulating cover layer 36 is removed by etching using the insulating cover layer 36 as an etching resist, and then a terminal is formed on the surface of the terminal portion 38 by electrolytic plating.